1. Field of the Invention
The invention relates to a system for recording and/or reading an information signal on a track of an optically readable record carrier on which track a position-identifying signal which is synchronous with a clock signal is recorded by modulation of the track in accordance with the position-identifying signal. The system comprises optical scanning means for scanning the track with a radiation beam, an optical detector for detecting the radiation beam reflected by the track and for generating a detection signal which is representative of the modulation of the radiation beam caused by the track modulation, and a detection circuit for extracting the position-identifying signal from the detection signal.
The invention also relates to such a record carrier and to a method and apparatus for manufacture thereof.
2. Description of the Related Art
A system as described above is disclosed in British patent specification GB No. 2,069,219, which corresponds to pending U.S. application Ser. No. 110,063, which is a continuation of U.S. application Ser. No. 134,392, now abandoned, all of which are assigned to the present assignee.
The system described therein utilizes a record carrier in the form of an optically readable disc provided with a spiral grooved track comprising information areas which alternative with synchronization areas. The information areas are for recording information, whilst the synchronization areas provide control information for controlling the recording process by means of a preformed track modulation. This control information comprises inter alia position information in the form of an address of an information area adjoining the synchronization area. If by means of the recording and/or read apparatus information is to be recorded in an information area having a specific address, the addresses of the adjoining synchronization areas are read by scanning the synchronization areas with the radiation beam. The information area where the information is to be recorded is located with the aid of the addresses thus read.
Although a specific track portion in which the information signal is to be recorded can be located by means of this known system, it has the drawback that the successive information areas are interrupted by the synchronization areas.
This is a disadvantage, particularly if EFM-modulated information is to be recorded. For in such recording an uninterrupted information area is desirable.